We have focused on the role of the pituitary gland in the regulation of aldosterone secretion in an effort to localize the area where the unidentified hormone(s) is derived. Our studies presentlyinvolve the aldosterone response to dietary sodium restriction, ACTH administration, and angiotensin II infusion in experimental animals following surgically removal of (1) the entire pituitary gland, (2) the anterior pituitary gland, (3) the posterior pituitary gland, and (4) transection between the pituitary gland and the hypothalamus.